New Properties of Secondary Cosmic-Ray Lithium, Beryllium and Boron - - PowerPoint PPT Presentation

New Properties of Secondary Cosmic-Ray Lithium, Beryllium and Boron Measured by AMS

• M. Paniccia (DPNC - University of Geneva, Switzerland)
• n behalf of the AMS Collaboration

Secondary Cosmic Rays

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Horandel Adv. Space. Res. 41 (2008) 442-463

Fe

C N O Li-Be-B Sc-Ti-V-Cr-Mn

Lithium, Beryllium and Boron, as well as elements in the sub-Fe group, are much more abundant in cosmic rays than in the solar system: they are not direct products of cosmic-ray sources

Lithium, Beryllium and Boron are mostly produced from collision of primary cosmic rays, such as Carbon and Oxygen, with the interstellar medium (ISM).

Secondary Cosmic Rays

2 Cosmic rays are commonly modeled as a relativistic gas diffusing into a magnetized plasma. Diffusion models based on different assumptions predict a Secondary/Primary ratio asymptotically proportional to Rδ. With Kolmogorov turbulence model a δ = -1/3 is expected, while Kraichnan theory leads to δ = -1/2. Galactic Disk ISS Galactic Halo Primary (p, He, C, O, …) Secondary (Li, Be, B, …)

3 If the hardening is related to propagation properties in the Galaxy then a stronger hardening is expected for the secondary with respect to the primary cosmic rays.

Secondary Cosmic Rays and origin of spectral breaks

If the hardening in CRs is related to the injected spectra at their source, then similar hardening is expected both for secondaries and primary cosmic rays.

• C. Evoli (2019)

See also Serpico J. Astrophys. Astr. (2018) 39-41

AMS CRs Chemical Composition

4 H He Li Be B C N O F Ne Na Mg Al Si P S Cl Ar K Ca Sc Ti V Cr Fe Ni Mn Co

AMS has collected > 144 billion cosmic rays up to today. With such a statistics secondary cosmic rays can be measured with high precision Analyzed Analysis in progress

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Identical above ~ 7 GV.

Lithium and Boron Fluxes

• M. Aguilar et al., Phys. Rev. Lett. 120 (2018) 021101

Lithium 1.9 M Boron 2.6 M

Identical above ~ 30 GV. Effect of unstable 10Be component.

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Beryllium and Boron Fluxes

• M. Aguilar et al., Phys. Rev. Lett. 120 (2018) 021101

Beryllium 0.9 M Boron 2.6 M

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• M. Aguilar et al. Phys. Rev. Lett. 120 (2018) 021101

Li, Be and B Fluxes in Kinetic Energy

Over the last 50 years, only a few experiments have measured the Li and and Be fluxes above a few GV. Typically, these measurements have errors larger than 50% at 50 GeV/n. For the B flux, measurements have errors larger than 15% at 50 GeV/n. AMS-02 has dramatically improved this situation: the total error on each of the fluxes is 3%–4% at 50 GeV/n.

[GV] R ~ Rigidity 30

2

10

2

10 × 2

3

10

3

10 × 2 ]

1.7

(GV)

• 1

sr

• 1

s

• 2

[ m

2.7

R ~ × Flux 1 2 3 4

3

10 × Helium Carbonx30 Oxygenx28 Lithiumx400 Berylliumx200 Boronx145

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• M. Aguilar et al. Phys. Rev. Lett. 120 (2018) 021101

Primary and Secondary Fluxes

Lithium (×200) Beryllium (×400) Boron (×145) Helium Carbon (×30) Oxygen (×28)

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Lithium Beryllium Boron Helium Carbon Oxygen

Deviate from single power law above 200 GV. Secondaries hardening is stronger.

• M. Aguilar et al., Phys. Rev. Lett. 120 (2018) 021101

Primary and Secondary Spectral Indices

AMS published high precision data of: Li/C, Be/C, B/C, Li/O, Be/O, and B/O. Data were fit with power laws in the rigidity intervals [60.3 GV – 192 GV] and [192 GV – 3300 GV]. All ratios show a hardening (~ 2σ), i.e. secondaries exhibit a stronger hardening than primaries.

• M. Aguilar et al., Phys. Rev. Lett. 120 (2018) 021101

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Li/C Li/O Be/C Be/O B/C B/O

Secondary/Primary Flux Ratios

Δγ = 0.13 ± 0.06 Δγ = 0.09 ± 0.07 Δγ = 0.09 ± 0.05 Δγ = 0.19 ± 0.06 Δγ = 0.15 ± 0.07 Δγ = 0.14 ± 0.05

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Δ Spectral Index

• 0.5
• 0.4
• 0.3
• 0.2

Li/C Be/C B/C

R ] V G [ ~ Rigidity

60

2

10

2

10 × 2

3

10

3

10 × 2

• 0.5
• 0.4
• 0.3
• 0.2

Li/O Be/O B/O

R ] V G [ ~ Rigidity

60

2

10

2

10 × 2

3

10

3

10 × 2

192 GV 192 GV

Combining the six secondary/primary ratios a global hardening at 192 GV

• f 0.13 ± 0.03 is observed. This observation favors the hypothesis that the

flux hardening is an universal propagation effect.

• A. E. Vladimirov et al., Astroph. J. 752 (2012) 68
• P. Blasi et al., Phys. Rev. Lett. 109 (2012) 061101
• N. Tomassetti, Phys. Rev. D 92 (2015) 081301(R)

…

• M. Aguilar et al., Phys. Rev. Lett. 120 (2018) 021101

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Secondary/Primary Spectral Indices

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Nitrogen Flux

ΦN = (0.090±0.002) × ΦO + (0.62±0.02) × ΦB Nitrogen 2.2 M

• M. Aguilar et al., Phys. Rev. Lett. 121 (2018) 051103

Cosmic-ray Nitrogen nuclei are partly primaries and partly secondaries. AMS-02 model-independent estimation of abundance at the source:

13 Preliminary AMS 7 years data. Please refer to the AMS forthcoming publication in PRL.

Prospects: Boron to Carbon ratio

H C Fe He

Prospects

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sub-Fe/Fe

H He Li BeB C N O F Ne Na Al P S Cl Ar K Ca Sc Ti V Cr Fe Ni Mn Mg Si Co

Conclusions

Using the first five years of AMS-02 data, Lithium, Beryllium and Boron fluxes have been measured from 1.9 GV to 3.3 TV, with 1.9M, 0.9M and 2.6M nuclei respectively with a typical accuracy of 3-4% at 100 GV. The three fluxes deviate from a single power law above 200 GV in an identical way. This hardening is larger than the one observed for primary species (He, C, O). The secondary/primary flux ratios Li/C, Be/C, B/C, Li/O, Be/O, and B/O were measured taking into account correlations on systematic errors. The secondary/primary flux ratios show an average hardening of 0.13 ± 0.03. These observations favor the hypothesis that the flux hardening is an universal propagation effect. The Nitrogen spectrum has been measured from 2.2 GV to 3.3 TV, with 2.2M events. The flux is described by the sum of a primary (Oxygen) and a secondary (Boron)

• component. The model independent N/O ratio at source of 0.09 ± 0.02 is derived.

The accuracy of the secondary cosmic ray nuclei fluxes will be significantly improved, in particular at the highest rigidities, during the lifetime of the ISS (to at least 2028) Heavier nuclei secondary fluxes will be measured, probing origin and propagation of cosmic rays at high mass and charge.

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